Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 55)

Data Highway Communication
Chapter 3
3Ć10
PLC/PLC–2 station numbers are octal, while PLC–3 input files have
decimal addresses. This means that PLC–3 input files with an 8 or 9 in
their address are not used for read/write access by a PLC/PLC–2 station.
The PLC/PLC–2 station can use either protected or unprotected
commands to access its assigned PLC–3 file. Note, however, that the
PLC/PLC–2 station cannot access its assigned file until that file is created
and allocated at the PLC–3. To create a PLC–3 file, use the CREATE
command described in the PLC–3 Programming Manual (publication
1775–801).
Note that it is possible to have two PLC–3 stations communicate with
each other as if they were PLC/PLC–2 stations. To do this, simply allocate
the appropriate PLC/PLC–2 buffer files in the PLC–3 stations and uses
the PLC/PLC–2 addressing format (section titled PLC/PLC–2 Address
Specifications, chapter 4) in the assignment commands. Similarly, a
computer can sent PLC/PLC–2 commands to a PLC–3 station by using
the appropriate message packet formats (Appendix A).
To allow as many as 4 remote stations to access the same PLC–3 input
file:
1. Enable the PLC–2 MASK option in the LIST function. PLC–2
MASK is option 6 on the Module Options menu.
2. Select station numbers 100
8
apart. For example, you could use
stations 010, 110, 210 and 310.
The stations will have access to the input file which matches the lower
two digits of these station numbers (input file 10 in this example). When
the 1775– KA module receives a PLC–2 type command, it masks the
upper octal digit in order to determine which input file to access. So
commands sent from stations 010, 110, 210, and 310 would all access
input file 10.